Process margin relaxation

ABSTRACT

Process margin relaxation is provided in relation to a compensated-for process via a first optical device, fabricated to satisfy an operational specification when a compensated-for process is within a first tolerance range; a second optical device, fabricated to satisfy the operational specification when the compensated-for process is within second tolerance range, different than the first tolerance range; a first optical switch connected to an input and configured to output an optical signal received from the input to one of the first optical device and the second optical device; and a second optical switch configured to combine outputs from the first optical device and the second optical device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 17/305,287, filed Jul. 2, 2021, which is a continuation of U.S.patent application Ser. No. 16/862,262 filed Apr. 29, 2020, which issuedon Aug. 10, 2021 as U.S. Pat. No. 11,089,391. The aforementioned relatedpatent applications are herein incorporated by reference in theirentireties.

TECHNICAL FIELD

Embodiments presented in this disclosure generally relate to componentfabrication in optical or photonic devices. More specifically,embodiments disclosed herein relate to relaxing or expanding thefabrication process margins to handle variable or unpredictablemanufacturing tolerances in various fabrication processes.

BACKGROUND

The fabrication of photonic devices and the components thereof onPhotonic Integrated Circuits (PICs) are affected by variousmanufacturing techniques, and may be constrained by the tolerances inthose techniques. These tolerances can vary from layer to layer in afabricated device. For example, silicon photonic devices fabricated onSilicon On Insulator (SOI) wafers can include a device layer (fabricatedon a Si or other semiconductor layer) with a variation in thickness ofroughly X %, but can include other deposited or bonded layers (e.g., aSiN waveguide layer) with variations in thickness of roughly ±X nm. Thedifferences in tolerances, and the sensitivity to variation thatdifferent layers have can lead to stacking tolerances that, althoughevery individual layer is within manufacturing tolerances, the overalleffectiveness of the fabricated device is out of tolerance; leading tolow yields in the manufacturing process, devices that performsub-optimally, and/or difficult-to-scale construction processes toreduce the tolerances.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate typicalembodiments and are therefore not to be considered limiting; otherequally effective embodiments are contemplated.

FIG. 1 illustrates a two-way architecture of a selective photonicelement to improve the yield of photonic device fabrication, accordingto embodiments of the present disclosure.

FIG. 2 illustrates a three-way architecture of a selective photonicelement to improve the yield of photonic device fabrication, accordingto embodiments of the present disclosure.

FIG. 3 illustrates a four-way architecture of a selective photonicelement to improve the yield of photonic device fabrication, accordingto embodiments of the present disclosure.

FIG. 4 illustrates a multiplexed two-way architecture of a selectivephotonic element to improve the yield of photonic device fabrication,according to embodiments of the present disclosure.

FIG. 5 illustrates a Bragg grating multiplexed two-way architecture of aselective photonic element to improve the yield of photonic devicefabrication, according to embodiments of the present disclosure.

FIG. 6 is a is a flowchart of a method of fabrication and deployment fora selective photonic element, according to embodiments of the presentdisclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially used in other embodiments withoutspecific recitation.

DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

One embodiment presented in this disclosure is a photonic element,comprising: a first optical device, fabricated to satisfy an operationalspecification when a compensated-for process is within a first tolerancerange; a second optical device, fabricated to satisfy the operationalspecification when the compensated-for process is within secondtolerance range, different than the first tolerance range; a firstoptical switch connected to an input and configured to output an opticalsignal received from the input to one of the first optical device andthe second optical device; and a second optical switch configured tocombine outputs from the first optical device and the second opticaldevice.

One embodiment presented in this disclosure is a photonic element,comprising: an optical switch, including: a receiver arm; a first outputarm; and a second output arm; a first optical combiner, including: afirst primary input arm; a first secondary input arm; and a firsttransmitter arm; a second optical combiner, including: a second primaryinput arm; a second secondary input arm; and a second transmitter arm; afirst demultiplexer connected to the first output arm, the first primaryinput arm, and the second primary input arm, wherein the firstdemultiplexer is configured to satisfy an operational specification whena compensated-for process is within a first tolerance range; and asecond demultiplexer connected to the second output arm, the firstsecondary input arm, and the second secondary input arm, wherein thesecond demultiplexer is configured for to satisfy the operationalspecification when the compensated-for process is within a secondtolerance range, different than the first tolerance range.

One embodiment presented in this disclosure is a method, comprising:fabricating an optical switch; fabricating, according to a firsttolerance range of a compensated-for process, a first optical device incommunication with a first splitter arm of the optical switch;fabricating, according to a second tolerance range of thecompensated-for process that is different than the first tolerancerange, a second optical device in communication with a second splitterarm of the optical switch; fabricating an optical combiner with a firstcombiner arm in communication with the first optical device and a secondcombiner arm in communication with the second optical device; performingthe compensated-for process; in response to testing the first opticaldevice and the second optical device, selecting one of the first opticaldevice and the second optical device performing to an operationalspecification for a photonic device based on the compensated-forprocess; and controlling the optical switch to direct optical signals toand the optical combiner to receive optical signals from the selectedone of the first optical device and the second optical device.

Example Embodiments

The present disclosure provides for relaxing or expanding thefabrication process margins to handle variable or unpredictablemanufacturing tolerances in various fabrication processes by allowingfor the selection between multiple optical devices pre-constructed toexhibit different tolerance ranges for a given fabrication process witha difficult-to-control-for fabrication tolerance. Various switching(including splitting and recombining) arrangements are provided forselecting one optical device of a plurality of optical devices that areconfigured to compensate for variances in a separate fabrication processto result in a photonic element that operates within its operationaltolerances. Accordingly, two or more optical devices are provided in aphotonic element with separate tolerance ranges, thus allowing afabrication tolerance for the other process to extend across the two ormore devices.

Stated differently, if a fabrication process has a fabrication range ofX-Z, and the optical devices cannot be constructed to operate properlyacross the whole fabrication range of X-Z, several individual opticaldevices are provided with smaller tolerance ranges to extend across therange of X-Z (e.g., X-Y and Y-Z), and one optical device is selected foruse depending on the output of the fabrication process. For example,consider a fabrication process for a semiconductor deposition processhas a fabrication range of 40-60 nanometers (nm) in thickness, and theoptical devices can be constructed to operate with thicknesses of thesemiconductor in 10 nm increments. Accordingly, a first optical devicemay operate according to specification when the thickness is between40-50 nm, but not operate according to specification when the thicknessis between 50-60 nm, but a second optical device is provided to operatein this 50-60 nm tolerance range. An operator or fabricator can selectwhich of these optical devices to use based on the thickness of thefabrication process to align the tolerances (e.g., use the first opticaldevice when the semiconductor deposition is between 40-50 nm, but usethe second optical device when the semiconductor deposition is between50-60 nm).

Although examples are given herein primarily with respect to thetolerance ranges being provided to compensate for variances in thicknessof another process (e.g., a thickness of a second wafer or a film bondedto a wafer in which the optical devices are fabricated, a thickness ofdeposition layer, a thickness resulting from a physical/chemical etch ofa material), the tolerance ranges can relate to other properties invarious embodiments. For example, a tolerance range can relate to rangesin dopant concentration, refractive index, component width (e.g., a sizein a different orientation than “thickness”), resistivity, inductance,capacitance, reflectivity, etc.

FIG. 1 illustrates a two-way architecture 100 of a selective photonicelement to improve the yield of photonic device fabrication, accordingto embodiments of the present disclosure. In the two-way architecture100, the selective photonic element includes an optical switch 110 andan optical combiner 140, a first optical device 120 a and a secondoptical device 120 b (generally, optical device 120; collectively,optical devices 120). The optical switches 110 and combiners 140 arecoupled to the optical devices 120 by 2×2 couplers 130 to definepotential light pathways running from the optical switch 110, throughone of the first optical device 120 a and the second optical device 120b, and outputting from the optical combiner 140.

The fabricator uses various optical switches 110 and combiners 140 tocontrol the input and output of optical signals through the selected(and not through the non-selected) optical devices 120. Depending on thearrangement and the components that the selective photonic element isconnected to that are not illustrated in the Figures, the selectivephotonic element may be one-directional (i.e., allowing for signaldirection in one designated direction) or bidirectional (i.e., allowingfor signal transmission in either direction). For ease of explanation,the present disclosure describes operation of the various photonicdevices herein for one-directional pathways moving from left-to-rightwhen viewing the Figures. But the present disclosure also covers usingright-to-left one-directional pathways (i.e., the opposite signalingdirection from what is generally given in the examples) andbidirectional pathways (e.g., substituting an understanding of asplitter/demultiplexer to operate as a combiner/multiplexer when used inreverse).

The optical switches 110 and combiners 140 may operate according tovarious schemas, including physical switches that route signals bylinking different input/output pairs, electro/magnetic switches that useelectromagnetic effects to route light, and thermally controlledswitches (e.g., Mach-Zehnder Interferometers) that phase shift pairedoptical signals to extinguish one optical signal and transmit another onoutput leads from the switch. For example, in a thermally controlledswitch, a received signal is split into two complementary signals, eachwith half of the original amplitude, which can be phase shifted relativeto one another so that when re-combined, the resulting output signal isequal to the original amplitude or reduced to zero. The phase shiftersin the thermally controlled switch heat the transmission medium in theswitch to control a level of phase shift on a given arm (e.g., between0-7 radians) and thereby the amplitude of the signals output from theoptical switches 110 and combiners 140.

When optical signals are received an optical switch 110 connected to aninput (e.g., via a receiver arm), the optical switch 110 is configuredas a splitter that outputs an optical signal received from the input toone of the first optical device 120 a and the second optical device 120b (e.g., via a respective output arm). The optical combiner 140 istherefore configured as a combiner that receives outputs from either ofthe optical devices 120 a-b (e.g., via respective input arms) and placesthe output onto a single shared transmission pathway (e.g., via atransmitter arm). To distinguish the various input/output arms of theoptical switches 110 and combiners 140, a first splitter/combiner can bedescribed as having a first primary, first secondary, first tertiary,first n-ary input arms or output arms, a second splitter/combiner can bedescribed as having a second primary, second secondary, second tertiary,second n-ary input arms or output arms, and an nth splitter/combiner canbe described as having an nth primary, nth secondary, nth n-ary inputarms or output arms as necessary to identify which splitter or combinera particular arm belongs to.

The optical devices 120, which can include various filters,multiplexers, demultiplexers, amplifiers, attenuators, lenses, taps(e.g., for probes to measure characteristics of the signal carrierthereon), microrings, optical resonators, splitters, optical modemultiplexers, 2×2 optical couplers, combined optical devices, etc., are,in one embodiment, the same type of device as one another, but areconstructed with different tolerance ranges. As the optical devices 120can include various passive devices, which are not powered or externallycontrolled or tuned after fabrication, the fabricated tolerance rangesof different optical devices 120 allow the operator or fabricator toselect (via the optical switches 110 and combiners 140) various rangesto use during operations, without having to expend power to tune anactive device. In some embodiments, the optical devices 120 includeactive devices, which are powered or externally controlled or tunedafter fabrication, but which may not be controllable/tunable across thefull fabrication range of the process being compensated for.

The tolerance ranges for the optical devices 120 indicate a fabricationrange that a given optical device 120 compensates for in relation to aseparate process of fabricating the photonic element. For example, whena first optical device 120 a is described as having a tolerance range of50-60 nm, the first optical device 120 a is not (necessarily)constructed to have a thickness of 50-60 nm, but rather is constructedso that a later process, if applied with a thickness of 50-60 nm to thefirst optical device 120 a, will result in the first optical device 120a passing operational tests.

As illustrated in FIG. 1 , the first optical device 120 a has atolerance range of A-B, and the second optical device 120 b has atolerance range of C-D to indicate that the optical devices 120 haveadjacent ranges. Either optical device 120 may offer the upper or lowerportion of the range and the fabricator can select between the opticaldevices 120 to select the given optical device 120 that offers atolerance range aligned with the result of the compensated-for process(e.g., satisfying an operational specification based on the outcome ofthe compensated-for process). The different ranges (e.g., A-B and C-D)discussed herein will be understood to include overlapping ranges (e.g.,where A>C>B>D), adjacent non-overlapping ranges (e.g., where, A>B=C>D),and non-adjacent non-overlapping ranges (e.g., where A>B>C>D) in variousembodiments. In each of the ranges discussed herein, A is a first upperrange value and B is a first lower range value (i.e., A>B for the firstrange A-B), and C is a second upper range value and D is a second lowerrange value (i.e., C>D for the second range C-D). As will beappreciated, tolerances can allow for the overlap of the nominallynon-overlapping ranges. For example, a first optical device 120 a and asecond optical device 120 b can have respective ranges of 40-50 nm and50-60 nm each ±5 nm, which could result in the first optical device 120a having a range of 35-55 nm and the second optical device 120 b havinga range of 45-65 nm.

In some embodiments, when the process that the differently-rangedoptical devices 120 are compensating for is centered at a given value(e.g., a film deposition displaying a normal distribution for thicknessover the toleranced range), the ranges and tolerances of the adjacentranges are selected so that both of the optical devices 120 cannominally operate at the centered value(s) for the compensated-forprocess. For example, with a process centered at a thickness of 50 nm±5nm (e.g., within 1σ of the centered value), the first optical device 120a may have a range of 40-52 nm±5 nm and the second optical device 120 bmay have a range of 48-60 nm±5 nm. Additionally or alternatively, thefabricator may select the ranges to (partially) overlap the opticaldevices 120 to so that if the compensated-for process is within thecenter of its range (e.g., within 1σ of the centered value) then eitheroptical device 120 could be selected to allow an operator to switchbetween the optical devices 120 based on operational conditions. Forexample, if the first optical device 120 a is originally selected foroperation, and thermally degrades over time due to use, an operator mayattempt to use the second optical device 120 b when the first opticaldevice 120 a falls out of tolerance, thus potentially extending theoperation lifetime of the photonic device.

Although the present disclosure primarily gives examples of thecompensated-for process being performed during the construction of theselective photonic element itself (including the optical devices 120thereof), in some embodiments, the differently ranged optical devices120 can be additionally or alternative configured to compensate forprocesses and tolerances of separately fabricated devices connected toor mated with the selective photonic element. For example, a selectivephotonic element can be constructed with two (or more) differentlyranged optical devices 120 that intentionally operate within differenttolerances, but are provided to compensate for an external opticaldevice (e.g., an optical transmitter). For example, a first opticaldevice 120 a can be selected when an optical transmitter operates withinspecification, while a second optical device 120 b can be selected whenthe optical transmitter operates out of specification (e.g., bringingthe optical signal back into specification for an optical receiver).Accordingly, the selective photonic element can be provided tocompensate for the fabrication processes of an external device and relaxthe process margins thereof by selecting the optical device 120 matchedto the operational profile of the separately fabricated external device(e.g., the optical transmitter).

FIG. 2 illustrates a three-way architecture 200 of a selective photonicelement to improve the yield of photonic device fabrication, accordingto embodiments of the present disclosure. In various embodiments, afabricator can construct three optical devices 120 a-c to select betweento compensate for the fabrication tolerances of the other fabricationprocess. The three-way architecture 200 includes the two-wayarchitecture 100, as discussed in greater detail in regard to FIG. 1 ,as well as a second optical switch 110 b, a second optical combiner 140b, and a third optical device 120 c.

The third optical device 120 c offers additional tolerance ranges fromthe first optical device 120 a and the second optical device 120 b.Although illustrated as having a range from E-F, it will be appreciatedthat the tolerance range of the third optical device 120 c can belocated to be below the tolerances ranges of the first and secondoptical devices 120 a-b (e.g., A-B>C-D>E-F), above the tolerance rangesof the first and second optical devices 120 a-b (e.g., E-F>A-B>C-D), orcentral to the tolerance ranges of the first and second optical devices120 a-b (e.g., A-B>E-F>C-D). In some embodiments, the third opticaldevice 120 c, which is handled by fewer optical switches 110 andcombiners 140 than the first or second optical device 120 a-b occupies aportion of the range of the compensated-for process that is seen mostoften in fabrication (e.g., the mean value and values seen within agiven standard deviation from the mean).

When selecting either the first or second optical device 120 a-b foruse, the fabricator activates the second optical switch 110 b to sendoptical signals to the first optical switch 110 a and activates thesecond optical combiner 140 b to receive optical signals from the firstoptical combiner 140 a. The two-way architecture 100 performs individualselection of the first or second optical device 120 a-b as is describedin relation to FIG. 1 .

When selecting the third optical device 120 c for use, the fabricatoractivates the second optical switch 110 b to send optical signalsthrough the third optical device 120 c and activates the second opticalcombiner 140 b to receive optical signals from the third optical device120 c. In various embodiments, the fabricator leaves the first opticalswitch 110 a and/combiner 140 a deactivated or configures the firstoptical switches 110 a and combiner 140 a to extinguish any residualsignals received from the second optical switch 110 b.

FIG. 3 illustrates a four-way architecture 300 of a selective photonicelement to improve the yield of photonic device fabrication, accordingto embodiments of the present disclosure. The four-way architecture 300can be understood as a two-way architecture 100 that includes two-wayarchitectures 110 a-b as the optical devices 120. The fabricator canchoose, via a second optical switch 110 b and a second optical combiner140 b, whether to route a signal through the first two-way architecture100 a or the second two-way architecture 100 b and select, via theselected two-way architecture 100 which optical device 120 to route thesignal through.

When selecting either the first or second optical device 120 a-b foruse, the fabricator activates the second optical switch 110 b to sendoptical signals to the first optical switch 110 a and activates thesecond optical combiner 140 b to receive optical signals from the firstoptical combiner 140 a. The first two-way architecture 100 a performsindividual selection of the first or second optical device 120 a-b as isdescribed in relation to FIG. 1 .

When selecting either the third or fourth optical device 120 c-d foruse, the fabricator activates the second optical switch 110 b to sendoptical signals to the third optical switch 110 c and activates thesecond optical combiner 140 b to receive optical signals from the thirdoptical combiner 140 c. The second two-way architecture 100 b performsindividual selection of the third or fourth optical device 120 c-d as isdescribed in relation to FIG. 1 .

By adding and removing hierarchies of optical switches 110 and combiners140 and optical devices 120, one will be able to create n-wayarchitectures to accommodate any number of optical devices 120. Whencreating an n-way architecture with an even number of optical devices120, several levels of two-way architectures 100 may be layered, such asto produce a four-way architecture 300 illustrated in FIG. 3 . Whencreating an n-way architectures with an uneven number of optical devices120, several levels of two-way architectures 100 may be layered, and atleast one layer includes a three-way architecture 200, such as isillustrated in FIG. 2 .

FIG. 4 illustrates a multiplexed two-way architecture 400 of a selectivephotonic element to improve the yield of photonic device fabrication,according to embodiments of the present disclosure. When the opticaldevices 120 are demultiplexers 410 (e.g., a first demultiplexer 410 aand a second demultiplexer 410 b) or multiplexers, the number of opticalswitches 110 and combiners 140 deployed by the fabricator on one side ofthe photonic element is greater than on the other side. For example,with a 4:1 demultiplexer 410, each demultiplexer 410 receives one input,and produces four outputs, each of which may carry data on a differentwavelength and/or at a different time division, and thus should beinterpreted separately. The first demultiplexer 410 a is manufacturedaccording a tolerance range of A-B while the second demultiplexer 410 bis manufactured according to a tolerance range of C-D.

Accordingly, the first demultiplexer 410 a and the second demultiplexer410 b are connected to an optical switch 110 on the input side(selectively receiving one input based on the operation of the opticalswitch 110) and output to each of the first through fourth opticalcombiners 140 a-d (also referred to collectively as the opticalcombiners 420), albeit with different signals extracted from the inputsignal to each of the optical combiners 420. As will be appreciated,other ratios of multiplexers and demultiplexers 410 can be used as theoptical devices 120 in the architectures discussed herein, with acorresponding number of optical combiners 140 making up the set ofoptical combiners 420. In various embodiments, each of the switches inthe optical combiners 420 is configured or tuned for operation toreceive signals of a different wavelength from the demultiplexers 410.Input arms for each of the optical combiners 420 are connected to thedemultiplexers and outputs of the optical combiners 420 are connected tovarious downstream components (e.g., photodetectors, light sources,wavelength-matched amplifiers, phase shifters (including thermal phaseshifters), wavelength shifters, separate transmission lines, additionaloptics, etc.).

By adding and removing hierarchies of optical switches 110 and combiners140 and optical devices 120, similarly to as in FIGS. 1-3 , one will beable to create multiplexed n-way architectures to accommodate any numberof optical multiplexers or optical demultiplexers 410 (generally,multiplexers or demultiplexers 410).

FIG. 5 illustrates a Bragg grating multiplexed two-way architecture 500of a selective photonic element to improve the yield of photonic devicefabrication, according to embodiments of the present disclosure. Whenthe optical devices 120 are demultiplexers 410 (e.g., a firstdemultiplexer 410 a and a second demultiplexer 410 b) or multiplexers,which can include various Bragg gratings 510 a-f (generally, Bragggrating 510) to split signal onto different arms, in variousembodiments. The Bragg gratings 510 a-c of the first demultiplexer 410 aare manufactured according a tolerance range of A-B while the Bragggratings 510 c-f of the second demultiplexer 410 b are manufacturedaccording to a tolerance range of C-D.

The first demultiplexer 410 a and the second demultiplexer 410 b areconnected to an optical switch 110 on the input side (selectivelyreceiving one input based on the operation of the optical switch 110)and output to each of the first through fourth optical combiners 140a-d, albeit with different signals extracted from the input signal toeach of the optical combiners 140 a-d. As will be appreciated, otherratios of multiplexers and demultiplexers 410 can be used as the opticaldevices 120 in the architectures discussed herein, with a correspondingnumber of optical combiners 140 making up the set of optical combiners.In various embodiments, each of the switches in the optical combiners140 a-d is configured or tuned for operation to receive signals of adifferent wavelength from the demultiplexers 410. Outputs of the opticalcombiners 140 a-d are connected to various downstream components (e.g.,photodetectors, light sources, wavelength-matched amplifiers, phaseshifters, wavelength shifters, separate transmission lines, additionaloptics, etc.).

In the Bragg grating demultiplexer two-way architecture 500 illustratedin FIG. 5 , the first demultiplexer 410 a includes a first Bragg grating510 a connected at an input to the optical switch 110, at a first outputto a first optical combiner 140 a, and a second output to an input of asecond Bragg grating 510 b. The second Bragg grating 510 b is in turnconnected at a first output to a second optical combiner 140 b and at asecond output to an input of a third Bragg grating 510 c. The thirdBragg grating 510 c, being the final Bragg grating 510 in the presentexample, is connected at a first output to a third optical combiner 140c and at a second output to a fourth optical combiner 140 d. Similarly,the second demultiplexer 410 b includes three Bragg gratings 510 d-farranged in a chain formation to sequentially demultiplex varioussignals from a combined signal received from the optical switch 110 tothe individual optical combiners 140 a-d. As will be appreciated, ademultiplexer 410 including Bragg gratings 510 for use in demultiplexingn signals from a combined signal includes n−1 Bragg gratings 510arranged in a chained formation.

By adding and removing hierarchies of optical switches 110 and combiners140 and optical devices 120, similarly to as in FIGS. 1-3 , one will beable to create multiplexed n-way architectures to accommodate any numberof multiplexers or demultiplexers 410.

FIG. 6 is a flowchart of a method 600 of fabrication and deployment fora selective photonic element, according to embodiments of the presentdisclosure. Method 600 begins with block 610, where the fabricatorfabricates the various optical switching elements (e.g., opticalsplitters and optical combiners) to select a given pathway through aselectable photonic element for light to be carried through.

At block 620 the fabricator fabricates a plurality of optical devices120 according to corresponding tolerance ranges (e.g., a first opticaldevice 120 a according to a first tolerance range, a second opticaldevice 120 b according to a second tolerance range, etc.). In variousembodiments, the optical devices 120 can include one or more of:switches, filters, multiplexers, demultiplexers, amplifiers,attenuators, lenses, taps, microrings, optical resonators, etc. As willbe appreciated blocks 610 and 620 may be performed with block 610occurring before block 620, after block 620, or contemporaneously withblock 620. The optical devices 120 are fabricated to be in communicationwith the various optical switching elements (e.g., splitter arms fromthe upstream optical switches 110, combiner arms of the downstreamoptical combiners 140), and the various switches 110 and combiners 140,when cascaded or arranged in a hierarchy are similarly fabricated to bein communication with one another.

At block 630, the fabricator performs the compensated-for process thatthe plurality of optical devices 120 fabricated per block 620 areconstructed according to various tolerance ranges to select against. Forexample, the compensated-for process includes bonding a wafer or film ofa material with a predefined thickness to the wafer in which the opticalswitches 110 and combiners 140 and optical devices 120 are fabricated,and/or etching a bonded, deposited, or grown layer on the wafer in whichthe optical switches 110 and combiners 140 and optical devices 120 arefabricated from a first thickness to a second (lesser) thickness tocontrol for the different effects of the variable thickness of thatmaterial on the optical devices 120. In various embodiments, thecompensated-for process is a part of the fabrication process of theoptical switches 110 and combiners 140 and/or the optical devices 120,and method 600 may iterate through block 610-630 as several layers ofmaterial are deposited, etched, encapsulated, etc.

At block 640, the fabricator tests the first optical device 120 a. Insome embodiments, the fabricator adjusts the switches 110 and combiners140 to direct a test signal through the first optical device 120 a todetermine whether the output signal indicates that the construction offirst optical device 120 a (e.g., according to the first tolerancerange) is aligned with the result of the compensated-for process appliedin block 630. In some embodiments, the fabricator measures the result ofthe compensated-for process applied in block 630 (e.g., a thickness of amaterial, a reflectivity of a surface, a conductivity of a material) andcompares the result against the tolerance range of the first opticaldevice 120 a to determine whether the two are aligned.

When the first optical device 120 a is aligned with the result of thecompensated-for process, method 600 proceeds to block 650, where thefabricator selects the first optical pathway and sets the switches 110and combiners 140 accordingly to direct optical signals into and out ofthe first optical device 120 a.

When the first optical device 120 a is not aligned with the result ofthe compensated-for process, method 600 proceeds to block 660, where thefabricator examines the next optical device 120 (e.g., a second opticaldevice 120 b). Similarly to block 640, the fabricator may test the givenoptical device 120 based on observing the quality of a test signalpassed through the given optical device 120 or by matching the result ofthe compensated-for process against the tolerance range of the givenoptical device 120.

When the given optical device 120 is aligned with the result of thecompensated-for process, method 600 proceeds to block 670, where thefabricator selects the given optical pathway associated with the givenoptical device 120 and sets the switches 110 and combiners 140accordingly to direct optical signals into and out of the given opticaldevice 120.

When the given optical device 120 (e.g., a second optical device 120 b)is not aligned with the result of the compensated-for process, method600 returns to block 660, where the fabricator examines the next opticaldevice 120 (e.g., a third optical device 120 c). When all of the opticaldevices 120 fabricated in the given photonic element have been tested,and none align with the result of the compensated-for process, method600 proceeds to block 680, where the fabricator rejects the photonicelement, which may be scrapped, recycled, or repurposed (e.g., for adifferent and/or more permissive operational specification).

In some embodiments, where the ranges of two or more optical devices 120overlap, method 600 can include testing all of the optical devices 120that have tolerance ranges that overlap and selecting the one opticaldevice 120 that best satisfies an operational specification for thephotonic element (e.g., the optical device 120 whose output ismost-centered in the range specified by the operational specification).In some embodiments, when multiple optical devices 120 satisfy theoperational specification, the fabricator can identify the other opticaldevices 120 that satisfy the operational specification (but were notselected as the “best” optical device 120) and indicate that suchoptical devices 120 may be used as backup or redundant components (e.g.,when the originally selected “best” optical device 120 thermallydegrades or is damaged).

In the current disclosure, reference is made to various embodiments.However, the scope of the present disclosure is not limited to specificdescribed embodiments. Instead, any combination of the describedfeatures and elements, whether related to different embodiments or not,is contemplated to implement and practice contemplated embodiments.Additionally, when elements of the embodiments are described in the formof “at least one of A and B,” it will be understood that embodimentsincluding element A exclusively, including element B exclusively, andincluding element A and B are each contemplated. Furthermore, althoughsome embodiments disclosed herein may achieve advantages over otherpossible solutions or over the prior art, whether or not a particularadvantage is achieved by a given embodiment is not limiting of the scopeof the present disclosure. Thus, the aspects, features, embodiments andadvantages disclosed herein are merely illustrative and are notconsidered elements or limitations of the appended claims except whereexplicitly recited in a claim(s). Likewise, reference to “the invention”shall not be construed as a generalization of any inventive subjectmatter disclosed herein and shall not be considered to be an element orlimitation of the appended claims except where explicitly recited in aclaim(s).

Aspects of the present disclosure are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatuses(systems), and computer program products according to embodimentspresented in this disclosure. It will be understood that each block ofthe flowchart illustrations and/or block diagrams, and combinations ofblocks in the flowchart illustrations and/or block diagrams, can beimplemented by computer program instructions. These computer programinstructions may be provided to a processor of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means for implementing thefunctions/acts specified in the block(s) of the flowchart illustrationsand/or block diagrams.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other device to cause aseries of operational steps to be performed on the computer, otherprogrammable apparatus or other device to produce a computer implementedprocess such that the instructions which execute on the computer, otherprogrammable data processing apparatus, or other device provideprocesses for implementing the functions/acts specified in the block(s)of the flowchart illustrations and/or block diagrams.

In view of the foregoing, the scope of the present disclosure isdetermined by the claims that follow.

We claim:
 1. A photonic element, comprising: an optical switch includinga first splitter arm and a second splitter arm; a first optical devicein communication with the first splitter arm, wherein the first opticaldevice satisfies a first fabrication tolerance range, wherein the firstfabrication tolerance range includes a first upper range value and afirst lower range value; a second optical device in communication withthe second splitter arm, wherein the second optical device satisfies asecond fabrication tolerance range, wherein the second fabricationtolerance range includes a second upper range value and a second lowerrange value, and wherein second fabrication tolerance range is differentfrom the first fabrication tolerance range; a first optical combinerwith a first combiner arm in communication with the first optical deviceand a second combiner arm in communication with the second opticaldevice, wherein the first optical combiner is configured to receiveoptical signals of a first wavelength from the first optical device andthe second optical device; and a second optical combiner, with a thirdcombiner arm in communication with the first optical device and a fourthcombiner arm in combination with the second optical device, wherein thesecond optical combiner is configured to receive optical signals of asecond wavelength that is different from the first wavelength from thefirst optical device and the second optical device.
 2. The photonicelement of claim 1, wherein the first optical device and the secondoptical device are one of demultiplexers or multiplexers.
 3. Thephotonic element of claim 1, wherein the optical switch, the firstoptical combiner, and the second optical combiner include thermal phaseshifters.
 4. The photonic element of claim 1, wherein the second upperrange value equals the first lower range value.
 5. The photonic elementof claim 1, wherein the second upper range value is lower than the firstlower range value.
 6. The photonic element of claim 1, wherein the firstfabrication tolerance range and the second fabrication tolerance rangeare set according to a fabrication process with a fabrication toleranceextending across the first fabrication tolerance range and the secondfabrication tolerance range that is greater than an operationaltolerance for the photonic element.
 7. A photonic element, comprising:an optical switch including a first splitter arm and a second splitterarm; a first optical device including a first input arm, a first outputarm, and a second output arm, wherein the first input arm is connectedto the first splitter arm, and wherein the first optical devicesatisfies a first fabrication tolerance range, wherein the firstfabrication tolerance range includes a first upper range value and afirst lower range value; a second optical device including a secondinput arm in communication with the second splitter arm, a third outputarm, and a fourth output arm, wherein the second input arm is connectedto the second splitter arm, wherein the second optical device satisfiesa second fabrication tolerance range, wherein the second fabricationtolerance range includes a second upper range value and a second lowerrange value, and wherein the second fabrication tolerance range isdifferent from the first fabrication tolerance range; a third opticaldevice including a third input arm, a fifth output arm, and a sixthoutput arm, wherein the third input arm is connected to the first outputarm, and wherein the third optical device satisfies the firstfabrication tolerance range; a fourth optical device including a fourthinput arm, a seventh output arm, and an eighth output arm, wherein thefourth input arm is connected to the third output arm, and wherein thefourth optical device satisfies the second fabrication tolerance range;a first optical combiner connected to the second output arm and thefourth output arm; a second optical combiner connected to the sixthoutput arm and the eighth output arm; and a third optical combinerconnected to the fifth output arm and the seventh output arm; whereinthe first optical device and the second optical device are respectivelyconfigured to output first optical signals in a first wavelength rangevia the first output arm and the third output arm and output secondoptical signals in a second wavelength range via the second output armand the fourth output arm; and wherein the third optical device and thefourth optical device are respectively configured to output thirdoptical signals in a third wavelength range via the fifth output arm andthe seventh output arm and output fourth optical signals in a fourthwavelength range via the sixth output arm and the eighth output arm. 8.The photonic element of claim 7, wherein the first optical device, thesecond optical device, the third optical device, and the fourth opticaldevice are Bragg grating multiplexers or demultiplexers.
 9. The photonicelement of claim 7, wherein the optical switch, the first opticalcombiner, the second optical combiner, and the third optical combinerinclude thermal phase shifters.
 10. The photonic element of claim 7,wherein the second upper range value equals the first lower range value.11. The photonic element of claim 7, wherein the second upper rangevalue is lower than the first lower range value.
 12. The photonicelement of claim 7, wherein the first fabrication tolerance range andthe second fabrication tolerance range are set according to afabrication process with a fabrication tolerance extending across thefirst fabrication tolerance range and the second fabrication tolerancerange that is greater than an operational tolerance for the photonicelement.
 13. A method, comprising: fabricating a first optical device ina first substrate to satisfy a first fabrication tolerance rangecomprising a first upper range value and a first lower range value;fabricating a second optical device in the first substrate to satisfy asecond fabrication tolerance range comprising a second upper range valueand a second lower range value; fabricating a first optical switch inthe first substrate connected to an input and configured to output anoptical signal received from the input to one of the first opticaldevice and the second optical device; and fabricating a first opticalcombiner in the first substrate configured to combine outputs from thefirst optical device and the second optical device.
 14. The method ofclaim 13, wherein the second upper range value equals the first lowerrange value.
 15. The method of claim 13, wherein the second upper rangevalue is lower than the first lower range value.
 16. The method of claim13, wherein the first fabrication tolerance range and the secondfabrication tolerance range are set according to a fabrication processwith a fabrication tolerance extending across the first fabricationtolerance range and the second fabrication tolerance range that isgreater than an operational tolerance for a photonic element includingthe first optical device and the second optical device.
 17. The methodof claim 13, further comprising: fabricating a third optical device inthe first substrate to satisfy a third fabrication tolerance range,different than the first fabrication tolerance range and the secondfabrication tolerance range; fabricating a second optical switch in thefirst substrate connected to an input and configured to output theoptical signal received from the input to one of the first opticalswitch and the third optical device, wherein the first optical switch isconnected to the input via the second optical switch; and fabricating asecond optical combiner in the first substrate configured to combineoutputs from the third optical device and the first optical combiner.18. The method of claim 13, wherein the first optical device and thesecond optical device are one of multiplexers or demultiplexers, furthercomprising: fabricating a second optical combiner in the first substrateconfigured to combine outputs from the first optical device and thesecond optical device; wherein the first optical combiner is configuredto receive optical signals of a first wavelength from the first opticaldevice and the second optical device; and wherein the second opticalcombiner is configured to receive optical signals of a second wavelengthdifferent from the first wavelength from the first optical device andthe second optical device.
 19. The method of claim 13, furthercomprising: fabricating a second optical combiner in the first substrateconfigured to combine outputs from the first optical device and thesecond optical device; fabricating a third optical combiner in the firstsubstrate configured to combine outputs from the first optical deviceand the second optical device; wherein the first optical deviceincludes: a first demultiplexer configured to receive the optical signalfrom the first optical switch and provide a first output of a firstwavelength to the first optical combiner and a second output including asecond wavelength and a third wavelength; and a second demultiplexerconfigured to receive the second output from the first demultiplexer andprovide a third output of the second wavelength to the second opticalcombiner and a fourth output including the third wavelength to the thirdoptical combiner; and wherein the second optical device includes: athird demultiplexer configured to receive the optical signal from thefirst optical switch and provide a fifth output of the first wavelengthto the first optical combiner and a sixth output including the secondwavelength and the third wavelength; and a fourth demultiplexerconfigured to receive the sixth output from the third demultiplexer andprovide a seventh output of the second wavelength to the second opticalcombiner and an eighth output including the third wavelength to thethird optical combiner.
 20. The method of claim 13, wherein the firstoptical switch and the first optical combiner include thermal phaseshifters.